Power Steering Pressure Switch: Testing and Inspection

Chart C-1E:

Wiring Diagram:

CIRCUIT DESCRIPTION:

The Power Steering Pressure Switch (PSPS) is normally closed to ground. Turning the steering wheel increases power steering oil pressure, and engine load. This causes the idle speed to change. The pressure switch will open before the engine load can cause an idle problem. Opening the switch causes circuit 495 to read battery voltage and the ECM will increase the idle air rate and retard the timing.

A pressure switch that will not open, or a grounded circuit 495 may cause the engine to stop when power steering loads are high.

A pressure switch that will not close, or a circuit 495 open, may affect idle quality.


TEST DESCRIPTION: The numbers below refer to circled numbers on the diagnostic chart.

1. This checks for an ECM voltage signal on circuit 495 and confirms that ground circuit 450 is OK.

2. Maximum resistance, or infinity, indicates an open switch.

3. Less than 1.0 ohm indicates that the switch is closed when the power steering pressure is high. Switch is faulty.

DIAGNOSTIC AIDS:

A pressure switch that will not open or circuit 495 grounded may cause the engine to stall at idle when power steering loads are high.

A switch that will not close or circuit 495 open will cause timing to retard at idle and may affect idle quality.